Foodstuff container

ABSTRACT

The invention relates to a recyclable, waterproof and heatable foodstuff container having a structural layer made of paper, paperboard, corrugated paper, bag stock, ream wrap, roll wrap, folding board, solid fiber, or combinations thereof, the structural layer is coated with a polyacrylate. The polyacrylate is preferably derived from a component selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, 2-ethyl methacrylate, and combinations thereof.

This application claims priority to U.S. provisional application Ser. No. 61/057,714, filed on May 30, 2008, which is hereby incorporated by reference in its entirety

TECHNICAL FIELD

This invention relates to a new class of materials to be used as substitutes for polyethylene and poly(ethylene terephthalate), commonly known as PET. Polyethylene and PET have many uses. For example, waterproof or water-resistant paper or paperboard can be made with polyethylene and PET coatings. Many products can be produced from such waterproof or water-resistant paper or paperboard, for example: dishes, trays or other containers. These products can be used, for example, in prepackaging foodstuffs that are to be reheated or cooked in a microwave oven.

BACKGROUND ART

Kirk-Othmer Encyclopedia of Chemical Technology, 3^(rd) Edition, Volume 24, Page 454, et seq. John Wiley & Sons, Inc., 1984., teaches that waterproof paper or paperboard, coated or laminated with a multi-thermoplastic material, such as high-density polyethylene, or coated with an aqueous latex solvent solution of a polymer include, among the commercially important thermoplastic products PET. The resulting paper or paperboard is useful for boxes, bags, drums, and case liners among other industrial products and packaging materials. Excellent barrier properties to water, oil, water vapor, oxygen, and some other gases make paper and paperboard coated with these resins especially valuable and flexible for use as packaging materials and boxes.

Ideally, these products would be recycled. However, PET is not recyclable when contained on paper and/or paperboard products (See, the aforementioned Kirk-Othmer, Volume 3, Pages 497-502). PET is not recyclable when in a mixture with paper and/or paperboard products. PET is not recyclable when layered with paper and/or paperboard products. Thus, a need exists to identify a suitable alternative for polyethylene and PET. Otherwise, timber resources will be further despoiled to create new or replacement products; scarce landfill space will be filled; and incineration of used paper products will cause further pollution.

DISCLOSURE OF INVENTION

The present invention provides a substitute for paper or paperboard products coated or laminated with multi-thermoplastic materials, such as polyethylene, or coated with an aqueous latex solvent solution of such materials, such as PET. The polyethylene and/or PET replacement coating, according to the present invention, is also useful for all types of paper, bag stock, ream wrap, roll wrap, corrugated, folding board, solid fiber, paper-based microwavable or conventional oven, food trays. According to the present invention, waterproof or water-resistant paper and paperboard products are formed by substituting an acrylic containing material for the polyethylene and/or PET previously utilized.

According to the present invention, acrylics or polyacrylates, which are preferably derivatives of acrylic acid (CH₂═CHCO₂H), or methacrylic acid (CH₂═CH(CH₃)CH₂H), can be made into polymeric substances to replace PET or polyethylene in products, such as waterproof or water-resistant paper and paperboard.

Such acrylics or polyacrylates can be used to prepare coatings and solution polymers and polymerization processes providing high yields of polymers in a form suitable for a variety of applications. The polymer products can be made to vary widely in physical properties through controlled variation in the ratios of monomers, employed in their preparation, cross-linking, and control of molecular weight. They share common qualities of high resistance to chemical environmental attack, excellent clarity, and attractive strength properties. In addition to acrylic acid itself, methyl, ethyl, butyl, isobutyl, and 2-ethyl acrylates are commercially manufactured on a large scale and are available at better than 98-99% purity.

Suitable cross-linking agents for the acrylates include compounds of zinc, such as zinc oxide solution. Zinc oxide solution is a fine suspension of zinc oxide particles usually in an aqueous vehicle. Many other compounds can be used as cross-linking agents. Preferably, at least one crosslinking agent is selected from the group consisting of zinc oxide, ammonium oxide, calcium oxide, calcium stearate, magnesium stearate, aluminum oxide, isostearate, magnesium oxide, stannous oxide, tungsten oxide, sodium tungstate, sodium tungstate dihydrate, titanium oxide, aluminum stearate, zinc octoate, zinc salts of fatty acids, zirconium oxide, calcium isosterate, calcium salts of fatty acids, magnesium salts of fatty acids, and aluminum salts of fatty acids.

In one embodiment of the invention, the cross-linking agent includes a salt (as described herein) plus a butyric acid and 5-carbon acids, such as isobolic 2-methyl buteric and N-valeric acid. Generally, the fatty acids are fatty acids of animal and/or vegetable fats and oils and would be exempt from kosher compliance, since the potential use of animal oils in the origin of the animal in question may be unspecified. In such cases, the inorganic substances would be preferred. It is considered within the scope of this invention to incorporate more than one substance to form the cross-linking agent. However, as used throughout this description and claims the term, “cross-linking agent” includes the above-described compositions as well as heat, radiation or any other method for initiation a cross-linking reaction in acrylic materials.

Commercially available suitable cross-linking agents include ZINC OXIDE SOLUTION NO. 1, available from Johnson Wax Specialty Chemicals of Racine, Wis. The cross-linking agent is used in amounts sufficient to cross-link the acrylic material.

The acrylic materials of the present invention are preferably coated onto the paper or paperboard material in any of a variety of ways. For example, in making paper and kraft grades of liner, rolls of paper and kraft liners are unwound from a parent reel or a slit or slash winder into rolls of smaller size or feed into sheeters, such as cut-size sheeters. Two methods of coating boxes or other paper products are preferably utilized. The first method is identified as a curtain coating process. A completed board is passed through a curtain of emulsion of an acrylic as in the present invention in a procedure commonly known in the art of paper making as “curtain coating.” The face side of the board and the opposite side are coated with the emulsion. The second coating process is “cascading.” The cascading procedure is different from the curtain coating procedure in that a regularly corrugated box of any shape or size can be placed on one end, such that the corrugated flutes are vertical, to allow the emulsion to permeate the entire structure with the acrylic emulsion cascading around and through the container in a flat position that is easy to stack for shipping. Other methods of coating include coating the paper or paperboard during the paper making process. For example, the paperboard during the paper making process or a paper or kraft grade of liner may be sprayed with an emulsion after the press section, but before the drying section of a typical paper making process or may be dipped into an emulsion such that in a typical size press or applied before or after the calendar section.

It should be understood that according to the present invention and throughout the specification and claims, “coating” means “coating” or “impregnation” unless otherwise indicated. The coatings of the present invention exhibit excellent resistance to penetration by oil, grease and other materials, but they also exhibit excellent release properties when utilized as trays or pans containing a flour or flour substitute foodstuff, eggs, pastas, and sauces and vegetables and/or meets with or without gravies or sauces. Thus, the present invention has a wide range of packaging of foodstuffs that may require heating, cooking, reheating, microwave and/or other ovens.

BRIEF DESCRIPTION OF DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims, and accompanying drawings where:

FIG. 1: shows a photograph, illustrating various releases of yellow cake and traditional fudge brownies as baked in baking trays;

FIG. 2: shows a photograph of Quiche baked in a tray having a 56 lb pine liner; and

FIG. 3: shows a photograph of trays made according to the present invention after release of the Quiche baked therein.

MODES FOR CARRYING OUT THE INVENTION

In the following examples, coatings and products are compared to give a wide variety of test conditions based on available samples. All tests were conducted using a 10 oz. round “pie pan,” six different coating compositions chosen are as follows:

-   -   1.) 56# Kraft w/Bake-Kote 48 RC (Spectra-Kote)     -   2.) 35# Kraft w/coating     -   3.) 35# Kraft w/coating     -   4.) Coating Laminated to 56# Kraft     -   5.) Coating Laminated to 56# Kraft     -   6.) Adhesive laminated, Gold PET w/Gloss Coating on PET

Yellow cakes and traditional fudge brownies were baked in two sample trays for each coating. There were no significant differences between samples 1, 2 and 3, but sample 1 seemed to stick slightly more than 2 and 3. Samples 4, 5 and 6 released product better than 1, 2 and 3. The location of each sample in the oven caused some different bake qualities and the samples that seem to be baked more completely such as sample 4, release the brownies and cakes very well. This was also the case with samples 5 and 6, but neither released as well as sample 4.

Sample 4, 5 and 6 have better release than samples 1, 2, and 3. Sample 4 had the best release, especially if well-baked. A summary of release properties can be found in FIG. 1.

A second battery of tests was conducted similar to the first round including a comparative example to PET. The coatings are as follows:

-   -   1.) 56# Kraft w/Bake-Kote 48 RC (Spectra-Kote)     -   2.) 56# Pine Liner     -   3.) Laminated to 56# Kraft     -   4.) 56# Pine Liner w/Gold Matte Coating on PET     -   5.) 56# Pine Liner w/Coating

Quiches were baked in two sample trays for each coating. There were no significant differences between samples 2-5, but sample 2 did have slightly more Quiche stuck in it. Sample 1 performed poorly, one of them barely released the Quiche at all. Much more grease soaked through Sample 1 than any of the other samples. All samples, except for sample 1, are acceptable coatings. FIG. 2 shows a photographic illustration of the sample 1, as compared to FIG. 3, which is a photographic comparison of the trays made according to the present invention after release of the product. 

1. A foodstuff container comprising a structural layer coated with a polyacrylate, wherein the structural layer comprises a component selected from the group consisting of paper, paperboard, corrugated paper, bag stock, ream wrap, roll wrap, folding board, solid fiber, and combinations thereof.
 2. The foodstuff container of claim 1, wherein the polyacrylate is derived from a component selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, 2-ethyl methacrylate, and combinations thereof.
 3. The foodstuff container of claim 1, wherein the polyacrylate is cross-linked.
 4. The foodstuff container of claim 1, further comprising a foodstuff.
 5. The foodstuff container of claim 4, wherein the foodstuff is selected from the group consisting of eggs, flour, flour substitutes, milk, milk substitutes, cream, cream substitutes, sugar, sugar substitutes, butter, butter substitutes, chocolate, chocolate substitutes, vanilla, vanilla substitutes, nuts, legumes, vegetables, cheese, gravies, sauces, oils, pastas, and combinations thereof.
 6. The foodstuff container of claim 4, wherein the polyacrylate prevents the foodstuff from sticking to the structural layer.
 7. The foodstuff container of claim 4, wherein the container is suitable to hold the foodstuff during a processing step selected from the group consisting of heating, cooking, reheating, microwaving, baking and combinations thereof.
 8. The foodstuff container of claim 7, wherein the polyacrylate prevents the foodstuff from sticking to the structural layer after the processing step.
 9. The foodstuff container of claim 1, wherein the container is water-resistant.
 10. The foodstuff container of claim 1, wherein the container is recyclable. 